Longlining is a fishing technique that uses a long main line, called a "mainline," with many shorter lines, or "branch lines," attached to it. Each branch line has a hook, allowing fishermen to catch various fish species over a large area. This method is often used in deep-sea fishing to target species like tuna and swordfish. While longlining can be effective, it also poses risks to marine life. Bycatch, which refers to the unintentional capture of non-target species such as sea turtles and sharks, is a significant concern. Efforts are being made to develop more sustainable practices to minimize these impacts.